Stansell, Nathan Derek
(2009)
RAPID CLIMATE CHANGE IN THE TROPICAL AMERICAS DURING THE LATE-GLACIAL INTERVAL AND THE HOLOCENE.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Till deposits, related to advances of mountain glaciers, and lake sediments record periods of abrupt warming and cooling during the Late Glacial interval (LG) (17,500 to 11,650 cal yr BP) in the northern tropical Andes. The synchronicity of temperature shifts in the tropical mountains and high northern latitudes during this period indicates that the low latitude atmosphere played a major role in LG abrupt climate change. Generally, the northern tropics are cold and dry when temperatures are lower in the North Atlantic region, and the opposite occurs during warm periods. The pattern of abrupt seesaw-like hemispheric temperature shifts, and the apparent link to tropical atmospheric dynamics, demonstrates the importance of low latitude circulation and water vapor feedbacks in rapid climate change. Geologic evidence from the precipitation-sensitive southern tropical Andes were used to reconstruct periods of ice advances and retreats during the Late Holocene. Neoglaciation in the Cordillera Raura of Peru began at ~3100 cal yr BP, marking a transition to a prolonged period of increased moisture transport to the Andes. The most extensive neoglacial advance took place locally during the Little Ice Age when conditions were both wetter and colder. The long-term, Holocene pattern of renewed ice cover in this region of the Andes was probably enhanced by astronomical forcing and convection-driven changes in moisture availability. Short-term glacial variability during the neoglacial was likely driven mostly by a combination of solar, atmospheric and oceanic processes. Lake sediments from the Pacific region of Nicaragua were used to record changes in the regional moisture balance during the late Holocene (~1600 cal yr BP to the present). Oxygen isotope values of calcium carbonate down-core identify periods of lake level fluctuations that resulted from changes in precipitation and evaporation rates. The driest regional conditions recorded in the isotope data are coincident with the onset of Little Ice Age cooling. This abrupt transition to more arid atmospheric conditions at 700 cal yr BP is consistent with other records from the northern tropics and subtropics that suggest hydrologic changes in the tropics were connected to high latitude climate variability during the late Holocene.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
| Creators | Email | Pitt Username | ORCID  |
|---|
| Stansell, Nathan Derek | nas12@pitt.edu | NAS12 | |
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| ETD Committee: |
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| Date: |
24 June 2009 |
| Date Type: |
Completion |
| Defense Date: |
27 March 2009 |
| Approval Date: |
24 June 2009 |
| Submission Date: |
15 April 2009 |
| Access Restriction: |
5 year -- Restrict access to University of Pittsburgh for a period of 5 years. |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Geology and Planetary Science |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
glacier mass-balance; Little Ice Age; neoglaciation; Nicaragua; paleoclimate; Peru; stable isotopes; Venezuela; Younger Dryas |
| Other ID: |
http://etd.library.pitt.edu/ETD/available/etd-04152009-090612/, etd-04152009-090612 |
| Date Deposited: |
10 Nov 2011 19:37 |
| Last Modified: |
15 Nov 2016 13:40 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/7200 |
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